Apparatus for burning spirit or similar liquid fuel



Jan. 18, 1966 K. o. A. BOlJ ETAL APPARATUS FOR BURNING SPIRIT OR SIMILAR LIQUID FUEL 2. Sheets-Sheet 1 Filed D60. 27, 1961 Jan. 18, 1966 K. o. A. BOIJ ETAL APPARATUS FOR BURNING SPIRIT OR SIMILAR LIQUID FUEL 2 Sheets-Sheet 2 Filed Dec. 27 1961 Patented Jan. 18, 1966 3,229,679 APPARATUS FOR BURNHNG SPIRIT R SIMILAR LIQUID FUEL Karl Oskar Arne Boij, Vasagatan 18, Tranas, Sweden, and Bertil Karl Axel Johansson, Tranas, Sweden; Ake Almquist, administrator of said Berti! Karl Axel Johansson, deceased, assignor to said Boij Filed Dec. 27, 1961, Ser. No. 162,368 Claims priority, application Sweden, Jan. 24, 1961, 700/61 Claims. (Cl. 126-38) The present invention relates to apparatus for burning spirit or similar liquid fuel and has for its object to provide apparatus of this kind combining simplicity of design with an extraordinary safety of operation.

The main constructional features and the advantages of the device according to the invention will appear from the detailed description hereinafter of a preferred embodiment thereof in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a spirit stove for camping purposes constructed in accordance with the invention;

FIGURE 2 is a vertical section through the stove, and

FIGURE 3 shows the fuel reservoir in position for refueling.

In the embodiment illustrated in the drawing, the fuel reservoir is in the form of a flat circular can 10 made of thin sheet-steel. The bottom wall of the fuel reservoir has cut centrally therein a circular opening 11 with an upwardly embossed edge forming a kind of hollow boss 12, and its top wall has cut therein a corresponding opening 13 having a downwardly embossed edge 14. The reservoir is filled with a mass which is capable of absorbing the spirit or similar liquid fuel. According to the drawing, this absorbent consists of two superposed circular discs 15 of mineral wool, preferably diabase wool, each formed with a centrally disposed opening, thereby forming a vertical passage or channel 16 through the absorbent. The diameter of this passage is slightly larger than that of the can openings. Interposed between the two mineral-wool discs is a thin circular disc 17 of mineral down. This disc, due to the fineness of its capillaries, acts as a kind of wick tending to suck up fuel from the surrounding coarser absorption mass. The ultimate purpose of the wick is to secure a more even distribution of the fuel to the regions surrounding the tubular passageway in which evaporation of fuel, mixing of evaporated fuel with combustion air, and combustion takes place. Experience has shown that the provision of an intermediate layer of mineral down in the bulk of coarser fibrous material does in fact improve combustion, but the precise explanation for this is not known. Possibly the favorable result has something to do with the particular manner of refilling the fuel reservoir illustrated in FIGURE 3. When filling liquid fuel into the reservoir in the manner illustrated, approximately only half of the volume of the absorbent mass becomes immediately saturated with fuel, the absorbed amount of fuel being thereafter comparatively slowly distributed over the entire volume of the mass through capillary action. The wick seemingly has an accelerating influence on said fuel distributing process. In addition, the wick 17 acts to facilitate ignition when there is only a little fuel left in the reservoir. Disposed immediately inside the top wall of the can is a piece of wire gauze 18 forming a system of relatively coarse distributing passageways for supplying liquid fuel to the absorption mass and for venting the same. Numeral 19 designates an inclined tube which is embedded in the absorption mass and extends from the vertical channel 16 upwardly in an inclined direction towards the wire gauze 18. This tube has for its purpose to facilitate refilling the reservoir with fuel, as will be explained hereinafter. Inserted in the top opening 13 of the can is a burner tube or flame guide 20.

The assembly thus far described is mounted in a sheetmetal box 21. The lid 23 of the latter, which is adapted to be swung open about hinges 22, has an opening 24 cut in it through which the tubular flame guide 20 projects upward a short distance. The diameter of the opening 24 is sufficiently large to cause a wide annular air space 25 to be formed around the burner tube. Disposed on the bottom wallof the sheet-metal box 21 is an air duct 26 which is rectangular in cross section and has cut in its top wall a circular opening having its edge embossed upwardly to form an upwardly projecting tubular boss 27 adapted to be surrounded by the tubular boss 12 of the fuel reservoir. For controlling the supply of air to the centrally disposed passage or channel 16 through the absorption mass 15, a damper 28 is mounted on the end of a lever 29 which is pivoted on a pin 30 and provided at its end projecting outwardly from the sheet-metal box 21 with a finger grip 31. 1

The air duct 26 continues at the rear of the box 21 in a vertically extending duct section 32, the latter being continued, in its turn, by a vertically extending duct section 33. The latter is carried by a vertically disposed rear sheet-metal wind shield 34 which is connected to the box by hinges 35 and can be folded down upon the hearth place or lid 23 when the stove is not in use. Numerals 36 and 37 designate two fold-down lateral wind shields made of sheet metal. The uppermost air-duct section 33 is closed at its top end but is provided in its front wall adjacent its top end with an air intake opening 38 and in its rear wall with an air-intake opening 39 disposed at a slightly lower level. An inclined baflle plate 40 inserted in the duct and terminating short of each lateral wall thereof prevents air from blowing directly across the duct, entering through one intake opening and leaving through the other one.

Ignition of the burner may be effected simply by entering a burning match from above into the vertical passage or channel 16 to touch the channel wall which is wetted with fuel. Owing to chimney draught, combustion-sustaining air will be drawn through the passageway 33, 32, 26 past the damper 28 and into the burner passage 16 within the absorption mass, where an incomplete combustion will take place which causes the formation of a flame projecting upward through the mouth of the tubular flame guide 20. Above said mouth the combustion will be completed by means of secondary air supplied in part by air flowing up through the annular space 25 from the interior of the box 21 which communicates with the ambient air through apertures 41, and in part by air flowing into the flame directly from its environment. The intensity of combustion can be regulated by adjusting the damper 28. If the flame should happen to be driven downward through the burner passage 16, for instance by a downwardly directed puff of wind, then the flame will be guided through the air supply duct 26, 32, 33 and directed to a point situated sufficiently high above the ground to avoid any risk of setting the support of the stove to fire.

When using the stove in windy weather causing the risk of extinguishing the flame, then, due to the action of the wind, a positive pressure will be created in the air supply duct, whereby the rate of air flow through the latter will increase, causing the flame to be thrown more forcefully against the bottom of the cooking vessel. Thus the amount of air supplied will adjust itself automatically in proportion to the existing requirements.

If the fold-down duct section 33 is missing, windcatching air intakes could, of course, be arranged directly on the duct section 32.

In case the spirit or other liquid fuel should contain impurities, such as denaturing agents, which have a tendency of collecting on the surface of the burner channel and form gradually therein an impervious surface layer, such layer may be easily burned away by permitting occasionally the spirit or the like contained in the absorbent to be fully consumed. The diabase or other mineral wool absorbent is capable of withstanding the high temperature then set up in the surface layer of the burner passage or channel.

To refill the fuel reservoir with fuel, this reservoir is removed from the box 2-1 and is turned on an edge, or upside down, so that a funnel 42 can be introduced into the short pipe 19, as shown in FIG. 3. Fuel dumped through the funnel 42 will flow down to the wire gauze 18, through the open work of which the fuel will be spread out over a large area, whereby it can be absorbed rapidly by the surrounding mineral-wool absorbent 15. By suitably dimensioning the spout of the refilling funnel 42 it is possible to ensure that fuel will not be filled at a more rapid rate than that corresponding to the maximum rate of fuel absorp tion of the absorbent. The refuelling method thus described ensures that the absorption mass will never oversaturate itself with fuel, so that there will be no danger of fuel leakage in any position of the fuel reservoir.

The degree of compression of the mineral wool filling or other absorbent filling is so selected as to ensure satu ration at a suitable value. In this manner the absorbent will hold the liquid fuel even in case the stove should leak or is stored on edge.

The burner flame is extinguished by the action of apply ing a cap, not shown, over the mouth of the tubular flame guide 20. Any condensate of fuel vapors forming in con nection with extinction of the burner flame is absorbed by a sheet 43 of asbestos or the like disposed on the bottom wall of the air supply duct 26.

The invention is not restricted to the embodiment illustrated in the drawing, various kinds of modifications being conceivable without departing from the scope of the invention. Thus, the fuel reservoir need not be made in the form of a circular can, it being possible, as well, to construct the same to be of square or rectangular shape, for example. In some cases a separate duct for supplying primary air to the burner passage can be dispensed with. Further modifications can be effected by those skilled in the art.

What we claim is:

1. An apparatus for burning liquid fuel comprising in combination:

(a) a fuel reservoir,

(-b) said fuel reservoir comprising a substantially flat metallic top wall, a substantially flat metallic bottom wall and outer side walls connecting the outer peripheries of said top and bottom walls,

(c) the top wall and bottom metal wall of said fuel reservoir each having an opening therein, said openings being substantially vertically aligned and centrally located,

(d) the space between the said openings in said top and bottom walls forming an open tubular passageway,

(e) the space within the said walls of said fuel reservoir and exterior of said tubular passageway being filled with a mass of fuel absorbent material,

(f) said mass of fuel absorbent material consisting of a fibrous inorganic heat resistive material such as mineral wool,

(g) the innermost exposed boundary of said mass of fibrous inorganic heat resistive material forming the walls of said tubular passageway that extends between the said spaced apart openings in said top and bottom wall,

(h) a metallic burner tube extending upwardly from the said opening in the top wall of the fuel reservoir, said burner tube being generally in axial alignment with said tubular passageway,

(i) said fuel reservoir being mounted within a box structure,

(j) the exterior walls of said fuel reservoir being spaced inwardly from the walls of said box structure a sufficient distance to form air passageways under, above and around a substantial portion of said fuel reservoir,

(k) an air inlet means in said box structure which is in communication with the lower end of said tubular passageway,

(l) valve means for controlling the flow of air to the lower end of said tubular passageway,

(in) said air inlet means in said box structure also be- 7 ing in communication with an air passageway which passes beneath the fuel reservoir and exits through an outlet in the lid of the box structure, said outlet being in spaced annular relationship to said metallic burner tube.

2. An apparatus according to claim 1 wherein said mass of fuel absorbent material consists of two superposed circular discs of mineral wool, preferably diabase wool, each disc having a central opening, and said two discs having interposed therebetween a third thin circular disc of mineral down, whereby said third thin circular disc, due to the fineness of its capillaries, acts as a wick tending to suck up fuel from the surrounding coarser absorption mass.

3. An apparatus according to claim 1 wherein said box structure is provided with an upstanding wind shield, and

at least a part of said air inlet means being located within said wind shield.

4. A fuel reservoir unit comprising:

(a) a top metal wall section, a bottom metal wall section and outer side walls connecting the outer peripheries of said top and bottom walls,

(b) said top wall having a centrally located opening therein,

(c) an open tubular passageway extending downwardly from said centrally located opening in said top wall toward said bottom wall,

(d) an air inlet in communication with said open tubular passageway,

(e) the space within the said walls of said fuel reservoir and exterior of said open tubular passageway being filled with a mass of fuel absorbent material,

(f) said mass of fuel absorbent material consisting of a fibrous, inorganic, heat resistive material,

(g) the innermost boundary of said fibrous, inorganic, heat resistive material forming a Vapor permeable wall for said open tubular passageway that extends downwardly from said centrally located opening in said top wall.

5. A fuel reservoir according to claim 4 wherein said mass of fibrous fuel absorbent material is mineral wool.

6. An apparatus according to claim 4 wherein said mass of fuel absorbent material consists of two superposed circular discs of mineral wool, preferably diabase wool, each disc having a central opening, and said two discs having interposed therebetween a third thin circular disc of mineral down, whereby said third thin circular disc, due to the fineness of its capillaries, acts as a wick tending to suck up fuel from the surrounding coarser absorption mass.

7. A fuel reservoir in accordance "with claim 4 wherein an inclined fuel supply tube is provided within the interior of the fuel reservoir, the inlet end of said inclined fuel supply tube opening into said tubular passageway and the outlet end of said inclined fuel supply tube opening into the interior of the mass of fibrous fuel absorbent material.

8. A fuel reservoir according to claim 4 wherein said fuel reservoir unit is mounted within a box structure and spaced therefrom so as to form air passage means leading to said tubular passageway.

9. An apparatus as set forth in claim 4 having disposed immediately beneath the said top metal wall a piece of wire gauze forming a system of relatively coarse distribut- 5 ing passageways for fuel supplied, as well as for venting the absorbent.

10. An apparatus as set forth in claim 9 wherein the said top opening in said top metal wall has an in-turned edge adapted, in the inverted refueling position of the fuel container, to form a fuel collecting cup which communicates with the system of passageways formed by the said wire gauze.

References Cited by the Examiner UNITED STATES PATENTS 1,065,834 6/1913 Pike 15896 1,879,955 9/1932 Smith 126-43 2,130,434 9/1938 Solomon 15897 2,733,705 2/1956 Goulding 12693 X 2,804,132 8/1957 Mallory 15'896 2,852,016 9/ 1958 Weatherwax 126-38 X 10 JAMES W. WESTHAVER, Primary Examiner.

PERCY L. PATRICK, FREDERICK L. MATTESON JR., Examiners. 

4. A FUEL RESERVOIR UNIT COMPRISING: (A) A TOP METAL WALL SECTION, A BOTTOM METAL WALL SECTION AND OUTER SIDE WALLS CONNECTING THE OUTER PERIPHERIES OF SAID TOP AND BOTTOM WALLS, (B) SAID TOP WALL HAVING A CENTRALLY LOCATED OPENING THEREIN, (C) AN OPEN TUBULAR PASSAGEWAY EXTENDING DOWNWARDLY FROM SAID CENTRALLY LOCATED OPENING IN SAID TOP WALL TOWARD SAID BOTTOM WALL, (D) AN AIR INLET IN COMMUNICATION WITH SAID OPEN TUBULAR PASSAGEWAY, (E) THE SPACE WITHIN THE SAID WALLS OF SAID FUEL RESERVOIR AND EXTERIOR OF SAID OPEN TUBULAR PASSAGEWAY BEING FILLED WITH A MASS OF FUEL ABSORBENT MATERIAL, (F) SAID MASS OF FUEL ABSORBENT MATERIAL CONSISTING OF A FIBROUS, INORGANIC, HEAT RESISTIVE MATERIAL, (G) THE INNERMOST BOUNDARY OF SAID FIBROUS, INORGANIC, HEAT RESISTIVE MATERIAL FORMING A VAPOR PERMEABLE WALL FOR SAID OPEN TUBULAR PASSAGEWAY THAT EXTENDS DOWNWARDLY FROM SAID CENTRALLY LOCATED OPENING IN SAID TOP WALL. 